This invention relates to food processing, and more particularly, to reducing microbe content in processed foodstuffs. The invention encompasses both an apparatus and method for manipulating the pH of foodstuffs and then physically manipulating the foodstuffs to reduce microbe content.
Most foods are processed in some way before reaching the consumer. For example, vegetables may be washed, trimmed, blanched, and than frozen prior to distribution. Meat products also require significant processing before reaching the consumer. At the very least, the animal carcass is cut into segments and the larger cuts of meat or fillets are cut from these initial segments. Other usable elements remaining after separating the larger cuts of meat are then separated from the remaining unusable elements such as bone and then ground or chopped, mixed, and then commonly frozen for distribution.
Foodstuffs are inevitably exposed to microbes as the foodstuffs are processed or handled. Microbes are part of the natural decay process of organic material and may be deposited on foodstuffs through the air or by contact between the foodstuff and contaminated equipment or other material. Although some microbes may be relatively benign, others contribute to spoilage and some can cause serious illness. Lactic acid producing bacteria are examples of benign microbes, while some strains of E. Coli, Salmonella, Listeria, and Staph bacteria are examples of pathogenic microbes which can cause serious illness when ingested by humans.
Even with careful processing practices, foodstuffs may be exposed to pathogenic microbes during processing or initial handling. The risk of illness from dangerous microbes which may be present in foodstuffs is reduced by a careful handling and cooking by the consumer. In larger cuts of meat for example, dangerous microbes may only be present on the surface of the meat and are readily killed in the cooking process.
Ground or chopped and mixed foodstuffs, including ground beef, may carry dangerous microbes which are killed only after thoroughly cooking the material. The reason for this is that dangerous microbes residing at the surface of a larger piece of the foodstuff may be distributed throughout the final ground or chopped product as the large piece is ground and mixed together with other pieces. Thorough cooking is required in order to kill microbes residing in the center of a piece of ground and mixed foodstuff.
It is desirable to control the growth of microbes and reduce microbe content in foodstuffs. Microbe content and growth in foodstuffs may be reduced by applying chemical additives or preservatives to the foodstuff. These chemical additives or preservatives, however, may not be acceptable to consumers, or may have undesirable effects on foodstuffs.
Alternatively to chemical additives or preservatives, heat may be used to kill microbes in foodstuffs. However, heat processing or sterilization often has undesirable effects on the quality or characteristics of the foodstuff and may make the food product undesirable to the consumer.
It is a broad object of the invention to provide a method for reducing microbe content in foodstuffs, particularly meats, and to provide an apparatus for performing the method.
The method of the invention comprises modifying the pH of a foodstuff and then physically manipulating or applying stress to the foodstuff while the foodstuff is in a frozen state. The physical manipulation produces significant relative movement within the foodstuff. In this sense xe2x80x9crelative movementxe2x80x9d means movement between one point in the foodstuff and adjacent points in the foodstuff. While the mechanism by which the process reduces live microbe count is not fully understood, pH modification followed by physical manipulation according to invention has been shown to significantly reduce microbe content in the treated foodstuffs.
The process according to the invention may be performed as a continuous process or as a batch process. In either case, the pH of the foodstuff to be processed is first modified by suitable means. After the pH modification, the foodstuff is cooled by a suitable freezer to a process temperature no greater than or below the freezing point of the foodstuff to place the foodstuff in a frozen state. As used in this disclosure and the accompanying claims, the xe2x80x9cfreezing point of the foodstuffxe2x80x9d means the temperature at which ice crystals begin to form in the foodstuff to be processed. The frozen foodstuff is then formed into workpieces. A manipulating arrangement then manipulates the frozen workpieces to produce relative movement preferably throughout each workpiece. The manipulating arrangement may define a working area and operate to manipulate each workpiece as it passes or is drawn through the working area.
The pH of the foodstuff may be modified in any suitable manner. For example, a higher pH foodstuff such as lean finely textured beef may be mixed with a regular ground beef to modify the pH of the resulting mixture. The process of producing lean finely textured beef, which increases pH with respect to the starting material, also represents a suitable pH modifyng step. Also, a foodstuff may be placed in contact with NH3 (Ammonia) in gaseous or aqueous form to increase the pH of the foodstuff. U.S. patent application Ser. No. 08/803,322, now U.S. Pat. No. 5,871,795, the disclosure of which is hereby incorporated herein by this reference, discloses a pH modifying apparatus and method which may be employed in this invention. pH modification within the scope of the invention also encompasses decreasing pH. pH of a foodstuff may be decreased by placing the foodstuff in contact with a pH reducing material such as CO2, for example.
In one form of the invention, the manipulating arrangement comprises first and second spaced apart rollers, with the working area defined between the first and second rollers. The rollers are preferably driven in a counter-rotating fashion to draw a workpiece there between. The spacing between the first and second rollers is smaller than an initial thickness of each workpiece so that each frozen workpiece is compressed and allowed to spread out laterally as it passes between the rollers.
Each roller may include a plurality of the spaced apart longitudinal ridges. The ridged rollers may be rotated such that each ridge on one roller registers with the space between a pair of adjacent ridges on the opposite roller as the rollers are rotated, similar to the cogs of two intermeshed gears. However, the ridges preferably do not touch, but maintain a minimum clearance. This ridged roller form of manipulating arrangement has the advantage that the frozen workpiece not only spreads out laterally as it is drawn between the rollers but is also bent between the opposing ridges on the counter-rotating rollers.
Another form of manipulating arrangement within the scope of the invention comprises two opposing plates with a suitable actuator, or actuators, for pressing the opposing plates together. The process includes placing a plurality of workpieces between the two plates and then operating the actuator arrangement to press the plates together to significantly reduce the volume between the plates. The relative movement of the plates presses the previously frozen workpieces into a block of frozen material, In this arrangement, the desired relative movement in the workpieces occurs as the workpieces deform to fill the voids left between adjacent workpieces when the workpieces were initially placed in the area between the opposing plates.
Regardless of the particular manipulating arrangement employed to manipulate the frozen workpieces according to the invention, a manipulator temperature control system preferably controls the temperature of the manipulating arrangement surfaces which come in contact with the frozen workpieces. The manipulator temperature control system may cool the surfaces of the manipulating arrangement to ensure that heat from the surfaces of the manipulating arrangement does not raise the temperature of the workpieces to a temperature above the desired process temperature. Alternatively, the manipulator temperature control system may heat the manipulating arrangement surfaces and thereby heat the frozen workpieces from a lower process temperature to the freezing temperature or even slightly above the freezing temperature. Also, maintaining the surfaces of the manipulating arrangement at a temperature near the process temperature or slightly above the process temperature also helps prevent the workpieces from sticking to the manipulator surfaces.
These and other objects, advantages, and features of the invention will be apparent from the following description of the preferred embodiments, considered along with the accompanying drawings.